Embryology part 3

Question 1

What is stage 1 of the CVS development ?

Answer 1

From the lateral plate splanchnic mesoderm

• blood islands start to from all around the embryo forming the cardiogenic field
• Forms the heart tubes

Question 2

Name 3 examples of places where blood islands start to from

Answer 2

Yolk sac
Allantois
Connecting stalk and chorion

Question 3

What is stage 2 of the CVS development ?

Answer 3

The two heart tubes fuse and this forms the primordial CVS

Question 4

What stages 3 of the CVS development ?

Answer 4

Pericardial cavity is created which has developed from the intra-embryonic coelom. It has a membranes surrounding it which has two sides, the visceral side developed from splanchnic mesoderm ands the parietal side which has developed from somatic mesoderm.

Question 5

What is stage 4 of the CVS development ?

Answer 5

Embryo folds so that the primordial CVS is dorsal to the pericardial cavity

Question 6

What is stage 5 of the CVS development ?

Answer 6

The primitive heart tube starts to grow and develop. It grows to that it has 5 parts, the truncus arteriosus (cranial atrial end), the bulbus cordis, the primitive ventricle, the primitive atrium and the sinus venosus (caudal venous end).

Question 7

What is stage 6 of the CVS development ?

Answer 7

The heart tube grows and becomes surrounded by the pericardial cavity.

Question 8

What is stage 7 of the CVS development ?

Answer 8

The growing heart tube quickly runs out of space, especially the bulbs chords and ventricle which are growing fastest. So these two parts loop to the right pushing the ventricles left and down and the atria up and back. This forms the bulboventricular loop.

Question 9

What is the first congenital condition ?

Answer 9

Dextrocardia where the heart loops to the left

Question 10

What is stage 8 of the CVS development ?

Answer 10

Endocardial cushions grow from each side to create two atrioventricular canals. (A square in the middle which allow blood to pass into the atria on the left or right)

Question 11

What is stage 9 of the CVS development ?

Answer 11

The septum primum grows to separate the left and right atrium. The gap at the bottom is called the ostium primum however this will close. The top of the septum primum then breaks down and this part is called the ostium secundum. This creates a gap called the foramen ovule. The septum secundum also grown in and sits parallel to the septum primum it also has a hole but it is in a different place to the hole of the septum primum.
Foramen ovule allows blood to pass from the right atria to the left atria but will close. This happens when the two septum’s fuse and this may create a fossa ovalis.

Question 12

What is the 2nd congenital condition ?

Answer 12

PFO (patent foramen ovale) a type of ASP (atrial septal defect) where the foramen ovalis fails to close properly.

Question 13

What is stage 10 of the CVS development ?

Answer 13

A muscular ventricular septum grows up and forms the first half of the interventricular septum. It leaves a gap called the interventricular foramen.

Question 14

What is stage 11 of the CVS development ?

Answer 14

A aortopulmonary septum grows up in a spiral shape and divides the bulbis cordis and the truncus arteriosus into the aorta and pulmonary trunk.

Question 15

What is the 3rd congenital condition ?

Answer 15

Transposition of the great vessels allows gas exchange between the systemic and pulmonary circulation.
This can happen because the aortopulmonary septum fails to take its spiral course (See picture) or because the defective migration of the neural crest cells to the heart.
Transposition if often associated with a ASD or VSD as well and can cause cyanotic disease in new-borns.
Tetralogy of Fallot is a condition where there is a ASD, VSD, transposition and enlargement of ventricles.

Question 16

What is stage 12 of the CVS development ?

Answer 16

The bottom of the aortopulmonary septum fuses with the endocardial cushion to from a membranous interventricular septum which closes off the interventricular foramen.

Question 17

What is the 4th congenital condition ?

Answer 17

VSD Ventricular septal defects occur when there is a hole in the intraventricular septal

Question 18

What is stage 13 of the CVS development ?

Answer 18

Cusps, chordae tendineae and papillary muscles of the atrioventricular valves develop from the ventricular wall.
The semilunar valves (Pulmonary and aorta) grow from the subendocardial valve tissue.

Question 19

What is stage 14 of the CVS development ?

Answer 19

Cardiomyocytes are primitive pacemakers. In week 5 the SA node, AV node and bundle of His all start to develop. The AV node is in the interatrial septum.

Question 20

What is the 5th congenital condition ?

Answer 20

Failure of the conducting system to from properly causes SIDS

Question 21

What happens to the primitive aorta ?

Answer 21

It divides to form the right and left primitive aorta

Question 22

describe these left and right primitive aortas

Answer 22

They have a ventral and a dorsal end.

Question 23

How does the aortic sac from ?

Answer 23

When the ventral ends fuse and then it attaches to the truncus arteriosus and then the sac elongates and 6 aortic branches arise

Question 24

What happens to the first pair of arches ?

Answer 24

disappears

Question 25

What happens to the second pair of arches ?

Answer 25

disappears

Question 26

What happens to the third pair of arches ?

Answer 26

common carotid

Question 27

What happens to the fourth pair of arches ?

Answer 27

right becomes the right Subclavian arteries

left becomes the aortic arch

Question 28

What happens to the fifth pair of arches ?

Answer 28

disappears

Question 29

What happens to the sixth pair of arches ?

Answer 29

right and left pulmonary arteries and the ductus arteriosus.

Question 30

Describe 4 arch abnormalities

Answer 30

• Right subclavian comes from the left not the right and wraps around the trach and restricts it and the oesophagus
• Double aortic arch forms a thick circle around and restricts
• PDA where there is an abnormal connection
• Coarctation of the aorta which can be post or pre ductal

Question 31

What causes PDA?

Answer 31

Maternal rubella infection

Question 32

Name three vessels which become something in the adult

Answer 32

Vitelline vessels
umbicical vessels
cardinal vessels

Question 33

What do the vitelline vessels go onto supply in the adult ?

Answer 33

from the yolk sac to the gut vessels

Question 34

What does the umbilical vessels go onto supply in the adult ?

Answer 34

Placenta to the internal iliac

Question 35

What does the cardinal vessels go onto supply in the adult ?

Answer 35

from the body to the SVC and the IVC

Question 36

When does the lymphatic system develop?

Answer 36

at the start of the 6th week

Question 37

Describe the development of the lymphatic system

Answer 37

Six primary lymph sacs form
Lymph vessels will later join lymph sacs
thoracic duct develops from embryologic thoracic ducts. One gives rise to the upper third of the adult thoracic duct and one to the lower two thirds.

Question 38

What are the three foetal shunts?

Answer 38

The ductus venous shunts blood in the left umbilical vein directly into the IVC allowing oxygenated blood from the placenta to bypass the liver.
The foramen ovule shunts blood form the right atrium to the left atrium allowing blood to bypass the lungs.
The ductus arteriosus shunts blood from the right ventricle and pulmonary arteries to the aorta allowing the blood to bypass the lungs.

Question 39

What does the ductus venous become in the adult?

Answer 39

ligamentum venosum of the liver

Question 40

What does the foramen ovule become in the adult?

Answer 40

fossa ovalis

Question 41

What does the ductus arteriosus become in the adult?

Answer 41

the ligamentous arteriosum between the left pulmonary artery and the aorta and the umbilical arteries become the medial umbilical ligaments of the anterior abdominal wall